The present invention relates to a device for controlling operation of an internal combustion engine having a rotary shaft and means for sensing angular position of the shaft, the sensing means including a sensor disc arranged for joint rotation with the shaft and having on its periphery as many segments as many cylinders has the engine, and a stationary detector for detecting flanks of the segments, the detector generating signals applied to a control circuit for controlling ignition, and/or fuel injection and the like of the engine.
Prior art devices for controlling or regulating the operation of the engine of a motor vehicle, particularly the ignition, fuel injection and the like, employ sensor systems for detecting the angular position of a shaft of the engine, particularly of the crank shaft or of the cam shaft. Such sensor systems usually include sets of segments provided on the circumference of a sensor disc rotating jointly with the shaft. The number of the segments is proportional to the number of cylinders of the engine to provide markings extending over predetermined time intervals or angular ranges during the rotation of the shaft. For detecting the angular position of a crank shaft the number of the segments amounts to the half of the number of cylinders while for detecting the angular position of a cam shaft the number of the segments is equal to that of the cylinders because, as known, the crank shaft rotates with a doubled rotary speed of the cam shaft. Therefore, in the case of the cam shaft each segment is assigned to one cylinder, whereas in the case of a crank shaft each segment is assigned to two cylinders and the ingition or fuel ejection cycles are controlled in response to the passage of the flanks of respective segments by a fixed detector. The stationary detector reacts to the leading flange of each segment and by a suitable design of the length of respective segments the timing for the operation of the engine is controlled. However, sensor systems using segments of the same configuration have the disadvantage of limited application, namely they do not provide sufficient control in the case of a distributorless semiconductor ignition, or in the case of a two circuit high voltage distribution (for example in eight cylinder engines).
Known are also sensor arrangements in which individual segments are subdivided by a number of teeth and gaps between the teeth. Signals generated by the detector in response to the teeth and gaps are applied to a controlling circuit. The angular position of the shaft is determined by counting the circulating teeth or gaps. This arrangement is relatively expensive and requires additional counting devices. Moreover, if a segment is formed with a single tooth gap only, there is the risk of releasing additional ignition by the trailing edge of the gap.
From the German publication DE-OS No. 28,47,552.1 it is also known to shape all segments of a sensor disc in the form of sloping ramps whereby one of the ramps slopes in opposite direction than the remaining ramps. This known arrangement, however, has the disadvantage that the steep flanks of the ramps produced only needle-shaped pulses. For controlling the ignition of an internal combustion engine, however, it is desirable to provide switch-on pulses which have a different shape than switch-off pulses.
Furthermore, all prior art sensor devices upon starting the device require at least one rotation in order to recognize accurately the correlation of the markings.